VOGONS


First post, by infernalgr

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This is my first post here but i am a long time follower of the forum and it's great to now be a part of the community.

I'm in the process of selecting hardware to build a retro pc for dos/win98 gaming, i was looking at PII and PIII dual systems.
I'm aware that DOS and win98 do NOT support dual cpu's but my question is, is there a way to select which cpu to use in the bios or from a dip switch on the m/b? like A/B or both?

thank you.

Reply 1 of 11, by jheronimus

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I assume you want to be able to switch between CPUs with different speeds? In most (if not all) cases both CPUs need to be identical, so there would be no point switching between the two.

Last edited by jheronimus on 2019-08-12, 11:16. Edited 1 time in total.

Reply 2 of 11, by Scraphoarder

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In theory it may be possible with an adapter or interposer that physically could cut the power traces to the CPUs, but even if that could be done im not sure if a motherboard would accept a working CPU in slot/socket 2 if CPU 1 was not detected. Running two differnt CPUs at the same time i think isnt doable, but i read about a guy who had two different Xeon LGA 1366 CPUs in a board and they both worked at the speed of the slowest CPU.

Reply 3 of 11, by spiroyster

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Lemme guess...

You want to have a slower CPU in one slot, and a faster one in the other and be able to select which one to use (but not both at the same time) on boot?

I want to do this too, it would have to be a bios setting and I haven't found anything that would support CPU selection. I don't think its possible without some MacGuyver-isms 🙁

If you do find anything, please post here as I am interested in this also.

Reply 4 of 11, by infernalgr

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spiroyster wrote:
Lemme guess... […]
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Lemme guess...

You want to have a slower CPU in one slot, and a faster one in the other and be able to select which one to use (but not both at the same time) on boot?

I want to do this too, it would have to be a bios setting and I haven't found anything that would support CPU selection. I don't think its possible without some MacGuyver-isms 🙁

If you do find anything, please post here as I am interested in this also.

yes, i was thinking a PII@233 and a much faster PIII

After i posted about this i found another thread on this forum from 2017 i think about a similar question. People in the know said it would be quite tricky to pull that off. I suspect that this might be easier to do on a single slot motherboard with some kind of adapter(that doesn't exist).

Reply 5 of 11, by The Serpent Rider

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Could be impossible if a board requires to install the CPU in the first slot/socket.

I must be some kind of standard: the anonymous gangbanger of the 21st century.

Reply 8 of 11, by Big Pink

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There are combined Slot 1 + Socket 370 motherboards from when Slot 1 was being phased out in favour of PGA370.

Example: https://www.anandtech.com/show/491/22
A previous revision of the Tyan Trinity 400 had a jumper for controlling whether socket or slot was in use. Someone sufficiently technically-minded could create a switch so you don't have to open the case. That would be a great way to have a low PII and a high PIII on hand in the one box.

I thought IBM was born with the world

Reply 9 of 11, by mothergoose729

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Big Pink wrote:

There are combined Slot 1 + Socket 370 motherboards from when Slot 1 was being phased out in favour of PGA370.

Example: https://www.anandtech.com/show/491/22
A previous revision of the Tyan Trinity 400 had a jumper for controlling whether socket or slot was in use. Someone sufficiently technically-minded could create a switch so you don't have to open the case. That would be a great way to have a low PII and a high PIII on hand in the one box.

Does the computer boot with both the slot and the socket filled?

Reply 10 of 11, by Big Pink

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Alas, I don't know. The idea behind those boards was to give existing Slot 1 users an upgrade path to the higher clocked coppermines, so presumably only one would be filled at a time. Then again, if it needed a jumper setting it might be dumb enough to ignore the presence of another CPU.

I thought IBM was born with the world